The objectives of this project are twofold - 1) to determine the factors that control the movement of solute and water across the lung epithelium and 2) to elucidate the effects of airborne metals suchs as mercury and cadmium on these control mechanisms. Two biological preparations, the amphibian lung and the microlavaged, mammalian alveolar sac, will be utilized to pursue the objectives. Fluxes of ions, water and heavy metals across the entire lung wall and the luminal membrane of the alveolar epithelial cells will be measured in the excised bullfrog lung mounted as a planar sheet or as a sac. The effect of sulfhydryl compounds, EDTA and imidazoles on metal binding and metal-induced permeability changes will be measured in the intact, excised lung and in epithelial cells separated by enzymatic procedures. Similar measurements will be made by micropuncture techniques on the mammalian alveolar sac. Differences in the patterns of heavy metal protection afforded by luminal and blood-borne complexing agents may make it possible to differentiate between vascular and epithelial sites of metal action.